The present invention relates to a bar code reading apparatus for optically reading a bar code.
Hitherto, bar codes printed on packages of articles have ordinarily been dark black and lacking in brightness, while the background has been pure white having high brightness. For the purpose of properly reading such bar codes, bar code reading apparatuses have been specially designed. Many packages, however, are colored other than in the manner described above, i.e., the packages being of a dark color, creating the possibility that, should an equally dark bar code be printed on such a package, an erroneous reading will ensue. In the interest of preventing such erroneous readings many packages are specially designed and printed so as to include a designated white area on which a black bar code can be printed. Such specific printing, though it solves the problem of erroneous readings, only contributes to an increase both in the cost of printing and, ultimately, in the cost of the articles themseleves.
In consideration of such disadvantages, there are packages printed such that the package color is used as the background color of the bar code region. Consequently, by printing the bar code in a color having a brightness different from that of the background color, only two print colors are used, thereby reducing the print cost. Naturally, as described above, if the two print colors are white (background) and black (bar code), the given bar code can be read by a conventional bar code reading apparatus.
However, in some cases, packages of a dark color may be used so as to provide a more attractive article package, thereby being inappropriately designed for easy reading by a conventional bar code reading apparatus. There are, in fact, some packages in use whose background color is black and whose bar code and characters are printed in a gold color, such as, for example, packages of tobaccos made in the U.S.A. Similarly, some packages have a background color of drak gray or black and a bar code and characters of light gray or the like. Inevitably, the reading of such bar codes by a conventional bar code reading apparatus cannot be done accurately, inverted bar code being obtained as a result of the inversion of the usual background and bar code colors.